1. Field of Invention
The present invention relates to a decompression mechanism for an engine, and more particularly relates to an automatic decompression mechanism for an internal combustion engine. The automatic decompression mechanism selectively actuates a cylinder valve of the engine so as to reduce the compression pressure in the combustion chamber during starting of the engine, with results being that the starting force required to start the engine is reduced.
2. Description of Related Art
Automatic decompression mechanisms are typically employed in internal combustion (IC) engines to provide improved engine performance at a variety of engine speeds. Known mechanisms typically include a pivoting centrifugal component capable of varying an outside cam profile surface of a rotating cam gear when engine speeds are low, such as during the starting cycle of the engine. Such a centrifugal component is designed to selectively and temporarily open a cylinder valve of the engine during the starting cycle of the engine. If the cylinder valve is opened slightly and temporarily during the compression stroke of the starting cycle, it is helpful for decreasing the pressure in the cylinder and reducing the starting force required to start the engine. Once the engine is started and the engine is running at normal operating speeds, it is desirable to deactivate the decompression function so as to maximize engine power and reduce emissions.
Various decompression mechanisms of this type have been proposed in the art, for example as disclosed in U.S. Pat. Nos. 6,109,230; 6,343,582; and 5,943,992. One disadvantage of such prior art designs is that the assembled structures comprise a relatively large number parts, making the manufacture and assembly of the decompression mechanism relatively troublesome, and moreover making it difficult to reduce the cost and size of the mechanism.
It therefore would be desirable if a new automatic decompression mechanism were developed which employed a reduced number of parts and which was easily installed in combination with simple cam gear components. It further would be desirable if the new automatic decompression mechanism were to employ a simple cover member with an integrated biasing means adapted to retain the centrifugal member in the cam gear, and if the mechanism were to be relatively inexpensive to manufacture and assemble. Such a simple mechanism would also provide advantage by being more susceptible to automated assembly.